27 



Calculation of Quantity of Wood. 

 C L = 27-33 x -M^2= 1)431 c. ft 

 C 2 =11288x l ^j.= 5,885 

 C 3 =196-84x -^gj = 5,482 



12,798 = wood of stems. 

 Add 4% 552 = branches. 



Total Wood . 13,350 



Calculation of Average Stems. 

 5g = G'6171 sq. ft. and gi=38 in. 



124-843 - .10 rv A 



a 2 = -105- =1'1890 



120-226 



w gs= 



7. Survey by Girth-gradations. Methods of Draudt, Uriel, and 

 Ear tig. 



\Vhenever it is impossible to determine accurately the average 

 tree even for separate girth-classes, it is necessary to adopt as 

 the basis of survey girth-gradations (see page 13, I A ay), 

 which obviously require the measurement of a larger number of 

 sample stems than the method just described, the number for each 

 gradation being proportional to the total number of stems com- 

 prised in that gradation. 



Several methods of survey by girth-gradations have been 

 devised, but we will descri be here only those of Draudt, I 'rich, and 

 Robert Hartig : 



DRAUDT'S METHOD. 

 In this method a certain proportion, say the Mh part, of all the 



